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The Japanese bullhead shark is a docile, slow-swimming species that feeds mainly on shelled invertebrates and small bony fishes. Reproduction is oviparous, with females laying spiral-flanged eggs in communal "nests". This species is of little interest to fisheries.
From February to April, the females lay a maximum of 24 eggs two at a time once every 11–14 days, in water 2–13 m (6.6–42.7 ft) deep. [1] The egg case has two flanges spiraling around it, and thus may take the female several hours to deposit. [17] At first the case is soft and light brown, and over a few days it hardens and darkens in color.
The egg case genera Palaeoxyris and Fayolia, which are thought to have been produced by hybodonts and xenacanths respectively, two groups of extinct shark-like cartilaginous fish more closely related to modern sharks and rays than to chimaeras, resemble those of bulldog sharks in having a spiral collarettes running around them.
Females produce 10–16 eggs per year during late winter in July and August, though Michael (1993) noted that egg-laying may continue year-round. [1] The egg cases measure around 11 cm (4.3 in) in length, with a pair of thin flanges spiraling 6–7 times around the outside and two slender tendrils up to 2 m (6.6 ft) long at one end, used to ...
The Mexican hornshark (Heterodontus mexicanus) is a bullhead shark of the family Heterodontidae. This shark is grey-brown in color, with black spots scattered on the fins and body. It has a cylindrical trunk, conical head, and small spiracles behind the eyes. The snout of the Mexican hornshark is very round and blunt.
During this time, the female lays pairs of eggs every 8–17 days. [13] As many as eight pairs can be laid during this period. The eggs mature for 10–11 months before the hatchlings, known as neonates, can break out of the egg capsule. The eggs have been assessed in recent studies as having an 89.1% mortality rate, mostly from predation. [10]
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The smooth, cream-colored egg cases measure 12 cm (4.7 in) long, and have long, spiral tendrils at the corners that allow them to be fastened to underwater objects. [ 1 ] [ 9 ] Newly hatched sharks measure 16 cm (6.3 in) long; males and females mature sexually at 60 cm (24 in) and 80 cm (31 in) long respectively.